The Growth of Ovules. 75 



becomes a large seed and crowds the partitions of the pod to 

 one side along with the abortive ovules. Notice that the 

 carpels to which the undeveloped ovules belong do not 

 grow as much as the other one, thus making the fruit one 

 sided as shown in the drawing. The carpels split along 

 the midribs (m, m, m) when the pod opens. The midrib 

 of the fertile carpel splits smoothly, but the other two are 

 partly held together by the partitions which have been 

 forced against them. Do not fail to examine these fruits 

 and their seeds. Probably buckeyes once thousands of 

 years ago when the climate was different ripened all of 

 the ovules into small seeds. 



EXERCISE 42. 



The Growth of Ovules. You cannot study the 

 development of embryos from the beginning, without the 

 help of a compound microscope, but you can easily observe 

 all stages of growth from a tiny green speck to the full- 

 grown embryo. Most seeds are nearly full grown in 

 appearance before the embryo is more than fairly visible to 

 the naked eye. The seed coat, filled with a syrupy or 

 milky, usually sweet, liquid, appears to constitute the very 

 young seed. With a sharp knife cut in halves a great many 

 green-peas, in size from half-grown upward. You will 

 surely find in some of them tiny green embryos, and you 

 may get specimens from the size of a pin's head up to those 

 which tightly fill the seed coat. At the top of the figure is 

 seen magnified two diameters the young seed of a lupine, 



